In an update on the Equine Herpes Myeloencephalopathy outbreak in Los Angeles, two additional horses at the Los Angeles Equestrian Center were moved to quarantined isolation—one due to elevated temperature with pending Equine Herpes Virus (EHV-1) test results and the other with elevated temperature and confirmed positive for non-neuropathogenic EHV-1 nasal swab. Nine horses currently reside in quarantined isolation.
The three barns remain under quarantine with enhanced biosecurity and horses’ temperatures are monitored twice daily.
Since issuance of the quarantine on November 3, 2016 a total of six horses displaying neurologic signs have been confirmed positive for Equine Herpesvirus Myelencephalopathy. One of the six horses was euthanized on November 3rd due to the severity of clinical signs. All other confirmed positive horses remain in quarantined isolation and continue to stabilize and show improvement. Four of the six confirmed positive horses participated in a horseshow in Las Vegas, NV on October 24, -29, 2016. At this time, no additional EHV-1 cases have been confirmed in horses that exhibited at the Las Vegas horse show. The California Department of Food and Agriculture (CDFA) has confirmed that the host facility has taken biosecurity measures of thorough cleaning and disinfection of the show facility.
Equine Herpes Virus (EHV-1) infection in horses can cause respiratory disease, abortion in mares, neonatal foal death and neurological disease. The neurological form of the disease is known as Equine Herpes Myeloencephalopathy (EHM) and may be caused by damage to blood vessels of the brain and spinal cord associated with EHV-1 infection. EHM is most often due to the neuropathogenic strain of EHV-1, but may occasionally be caused by the non-neuropathogenic strain of the virus.
EHV-1 is easily spread and typically has an incubation period between 2-10 days. Respiratory shedding of the virus generally occurs for 7-10 days, but may persist longer in infected horses. For this reason, a twenty-one day isolation period of confirmed positive EHM cases is recommended along with stringent biosecurity protocols. Similar to herpes viruses in other species, the latent form of EHV-1 can reactivate at a later date, but generally with a low viral load posing a low risk of infecting other horses. Humans are not at risk of contracting the virus, however humans can act as an indirect mode of transmission.